Conventional security techniques are typically based on one or more factors such as something you know (e.g., a password), something you have (e.g., a key card), and something you are (e.g., biometrics). Geosecurity provides another factor: somewhere you are. More specifically, geosecurity involves the use of spatiotemporal information such as geographical position (and possibly time as well) as a factor in authentication. One application of geosecurity is to grant access to sensitive data only at authorized locations within a facility. Geosecurity techniques can also be used for a variety of other applications including generating alarms if a device is taken out of a secure area (i.e., geofencing), location-based control of device functionality (e.g., digital manners policy), proof of position, and location-enhanced social networking.
An desired property of any geosecurity application is that it should reliably reproduce a to unique geotag from any given location. This is a practical challenge, however, because geotags are customarily derived from radiofrequency (RF) signals that may not be reliable or may have limited stability or location accuracy. For example, the signal transmitters may be temporarily out of service or the signals may experience unpredictable fluctuations due to noise or interference from environmental effects or other RF transmissions.
Another important property of many geosecurity solutions is the cryptographic security of the geographical location information. It is desirable in many applications that the geotag can be made public while preserving the privacy of the location information from which it is derived. For example, encrypted geotags can be generated from location-dependent parameters of RF signals using one-way functions. However, unpredictable fluctuations in the RF signals can potentially alter the location-dependent parameters, resulting in a different encrypted geotag for the same location. Without the ability to reproduce unique geotags, valid locations will not be reliably authenticated (i.e., false rejection). One approach to reduce false rejection is to expand the geographical security radius of the geotags. However, geotags with a larger geographical security radius will match a wider range of geographical positions, risking positive authentication at undesired locations (i.e., false acceptance). Accordingly, there is a need for improved geosecurity methods and devices that address these problems.